Multiple bladed surgical cutting device removably connected to a rotary drive element

ABSTRACT

A cutting device for the cutting and reduction of matter from a surgical site having a cutting head having an entry tip and three or more cutting blades positioned on opposed leading edges of a window formed through the interior of the cutting head. The window includes angled walls extending from each cutting blade along the circumference of the window. The cutting head is attached to a shaft for mounting the cutting device to a rotary surgical drill. The cutting head can also have a blade on the outer perimeter of the head. The matter is removed and further reduced as the cutting head is rotated at the surgical site. The geometry of the cutting head and entry tip can be varied for particular surgical procedures. The cutting device can also include a cannula or drill guard.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of applicant's U.S. patentapplication Ser. No. 08/853,065, entitled "SURGICAL CUTTING DEVICEREMOVABLY CONNECTED TO A ROTARY DRIVE ELEMENT," filed May 8, 1997, whichis a continuation-in-part of U.S. patent application Ser. No. 08/695,984filed Aug. 15, 1996, now abandoned, which claims priority from U.S.Provisional Application No. 60/015,390 filed Apr. 12, 1996.

BACKGROUND OF THE INVENTION

This invention relates generally to devices used in surgical procedures,such as, for example, endoscopic diskectomy and endoscopic spinalfusion. More specifically, the invention relates to a rotatable surgicalcutting device which is removably connected to a rotary drive elementhaving a cutting head with three or more blades located on leading edgesof a window extending through the cutting head and spaced around acircumference of the cutting head.

FIELD OF THE INVENTION

In the United States, spinal disk problems are the most common cause ofdisability of people under 45 years of age. There are currently 5.2million Americans either temporarily or permanently disabled as a resultof chronic back pain. Approximately 220,000 spinal operations areperformed in America each year to combat the disabilities caused byspinal disk problems.

A common problem among patients suffering from chronic back pain is aprotruding lumbar intervertebral disc. This condition occurs when aportion of the disk protrudes into the spinal canal space and createspressure on a nerve. A patient may also experience a partial or completecollapse of an intervertebral disk, resulting in spinal instability,immobility and severe chronic pain.

It is often necessary to surgically remove offending disk material fromthe spinal canal to improve the spinal function of the patient and torelieve chronic pain. In some cases it is also necessary to perform aspinal fusion, to improve spinal stability and to provide additionalsupport for any damaged intervertebral disk. Also more recently, metalbone cages that are placed between intervertebral bodies have begun tobe utilized to improve the stability of the spine both during and afterthe fusion healing process.

Procedures such as endoscopic diskectomy can be used for the removal offibrous intervertebral tissue. Endoscopic surgeries are accomplished bycreating small openings or "ports" in the body, through which varioussmall instruments or a camera may be inserted and manipulated to observeor work in the disk space area. Current endoscopic procedures utilizedfor the removal of disk material rely primarily upon automated or manualmethods. (Surgical Dynamics Nucleotome or the Soframor-Danek Diskector).These methods remove intervertebral disk material by using a guillotinecutting blade, with the aspiration of disk material into a portconnected to a cannula, once the device is activated.

For open spinal fusions, products currently available for the removal ofintervertebral disk tissue include the Acromed manual PLIGinstrumentation and the Cloward PLIF set instrumentation. Theseinstruments are manual in operation and utilize rasps and rongeurs,whereby disk material is removed by increasing the size of the raspsequentially. Devices currently used for the preparation of theintervertebral disk space for bone cage placement are also manual inoperation, utilizing a traditional drill bit and brace or drill bithandle configuration.

Based upon the current instrumentation and procedures available for theremoval of intervertebral disk material and the preparation of bonegraft sites and bone cage placement, there remains an opportunity toimprove the speed, accuracy and effectiveness of these procedures. Inaddition, with the recent introduction of the bone cage technology, itis far more desirable to have the capacity to generate a circular voidin the intervertebral disk space for the placement of the bone cagerather than a void that is square, rectangular or cruciate in shape.Furthermore, animal studies have indicated that circular holes in theintervertebral disk space provide an improved response to healing overthose that are square, rectangular, or cruciate in shape. Therefore, anopportunity exists for the introduction of a device that will provide asmooth circular void in the intervertebral disk space in preparation forbone cage placement and allowing for improved healing of the annularopening.

Also due to the tenacious adhesion of the disk material to the vertebralend plate, an opportunity exists for a more efficient and effectivemethod of removing disk material from this area of the vertebra inpreparation for bone grafts.

Lastly, there remains an opportunity to reduce the amount of traumasuffered by the patient during back surgery, as the result of instrumentmovement and manipulation in and around the spinal canal and surroundingpathology.

SUMMARY OF THE INVENTION

The invention is a surgical cutting device constructed from one piece ofhardened surgical steel. Alternatively the cutting device can beconstructed of multiple parts braised or welded together. The device hasa proximal end comprising a mounting shaft, a main shaft, and optionaldepth indicators located on the main shaft. The device also includes acutting head positioned at the end of the main shaft at the distal endof the device.

The mounting shaft is designed to fit into most standard low or highspeed rotary surgical drills. The cutting device is attached to andremovable from the rotary drill in the same manner as currentlyavailable rotary tools and accessories, namely by placing the mountingshaft into the friction lock collet of the drill. The main shaft of thecutting device is designed in various lengths to enable the use of thedevice for both cannulated endoscopic surgeries, or non-cannulated openback surgeries. The main shaft can be a straight cylindrical shaft orcan be threaded similar to a screw which serves to move displacedemulsified disk material from the tip of the cutting device. Theoptional depth indicators provide a method for the instantaneousobservation of cutting depth when the device is in the intervertebraldisk space. These indicators also serve to alert the surgeon toover-penetration into the disk wall.

The cutting head of the device includes two, three or more cuttingblades and an entry tip. The multiple-bladed configuration of thecutting head forms a window between the cutting blades providing an areafor removed disk material to accumulate and be further reduced indensity.

The cutting head of the device is designed with various outsidediameters and tip configurations. The various head diameters allow forthe device to be used for the removal of disk material in the cervical,thoracic or lumbar regions of the spine, based upon the pathology andintervertebral disk space of the patient. The unique design of the headenables the smooth and accurate entry of the device into theintervertebral disk space, while simultaneously cutting and reducing thedensity of the removed intervertebral fibro cartilaginous disc material.The head of the device is also designed to perform decortication of boneif desired, either simultaneously or independently to the removal of thedisk material. Based upon the requirements of the surgical procedure,the surgeon may select one or more of the various tip configurations toperform the disk removal procedure. Also, by using a series ofincrementally increasing diameter heads, the surgeon can accuratelyincrease the size of the void created in the intervertebral disk space.This provides an evacuated disk space in preparation for a bone graft orthe placement of bone cage devices.

The head configurations of the device can be round, teardrop, bulb, orelliptical shaped or modified versions thereof, or notched or flameshaped. The various head configurations include one of a number ofdifferent entry tip configurations including a flat ended arrow styletip, a conical bullet style tip, an elliptical, circular, or rounded tipand modified versions thereof. The entry tip may also include anadditional cutting blade or blades to facilitate removal of tissue.These additional cutting blades can be a single blade, multiple blades,a raised spiral flute or helix circling the diameter of the head, or arasp configuration.

The bullet and arrow style tips are designed to be used primarily forthe initial entry into the intervertebral disk space. These tips providea smooth entry into the annulus of the disk, to begin the intervertebraldisk tissue removal process. The rounded tip is designed primarily to beused in a secondary operation, to increase the amount of disk materialremoved and to provide a smooth circular void in the disk. The tips ofthe devices may also be used for the decortication of bone if desired.Based upon the procedure to be performed, the location of the injury andthe position of the offending disk tissue, the surgeon will select thedevice head configuration, entry tip style and diameter accordingly.

The device may be used in a cannulated or non-cannulated fashion, basedupon the surgical procedure to be performed. For an endoscopic surgicalprocedure, the device is used in a cannulated fashion using a standardsurgical cannula and elongated guard that is designed to fit in mostsurgical cannulas currently available. When used in a cannulatedfashion, single, multiple or full length bushings or bearings can bepositioned on the shaft of the device to reduce the friction between theshaft and the cannula or guard. A mechanical depth stop can also beincorporated onto the shaft to protect the device from extending too farfrom the end of the cannula or guard when in use. The cutting device canbe made to be removable from or captive within the cannula or surgicalguard.

In the case of endoscopic surgeries, the device is placed through theskin and docked on the edge of the intervertebral disc. Once docked, thesurgeon uses the surgical drill to rotate the head of the device tosmoothly enter the annulus of the disc. As the device enters into thedisk space, the disk tissue is cut and migrates to the ellipticalopening at the center of the cutting head. As the procedure continues,the removed disk material is then further reduced in density, as aresult of the spinning of the cutting blades.

The surgeon may then use the device to decorticate the vertebral endplate in preparation for a bone graft, using the same, or a differentdevice diameter or tip configuration. Due to the reduction in density ofthe removed disk material, normal surgical irrigation and suction can beused to thoroughly flush the surgical site. Since the density of thedisk material is reduced to an emulsion, rather than being trimmed orcut into fragments, the possibility of disk debris being left at theoperation site is significantly reduced.

When used in open back surgery, the device is used in a non-cannulatedfashion, utilizing a guard. In the case of these surgeries, the deviceis used to remove disk tissue and decorticate bone externally from thecannula, in the same manner as described above for endoscopicprocedures.

In addition to spinal related surgeries, the surgical cutting device ofthe present invention is also applicable to other surgical procedures.For example, in hip surgery, the device can be used for the removal ofsoft tissue and the decortication of bone. In hip joint revisionsurgery, the device can be used for the removal of soft tissue, thedecortication of bone and the removal of bone cement. In shoulder andshoulder joint replacement surgery, the device is also applicable forthe removal of soft tissue and the decortication of bone. In kneesurgery and knee joint replacement surgery, the device can also be usedfor the removal of soft tissue and the decortication of bone. In alltypes of surgeries, the device will be attached to a rotary drill andoperate similarly to that in spinal surgery.

Additional procedures for which the device may be used include, but arenot limited to, the micro lumbar laminectomy, the anterior or posteriorinter-body lumbar diskectomy and fusion, the cervical anteriordiskectomy and fusion and the anterior thoracic diskectomy and fusionand the placement of bone cage devices between intervertebral bodies.

Accordingly, some objectives of this invention are to provide a surgicalcutting device capable of providing a circular hole in theintervertebral disk space for efficient disk removal during diskectomiesand in preparation for bone grafting and placement of bone cages;provide a surgical device with the ability to accurately remove andreduce the density of intervertebral fibro cartilaginous disk material,and therefore reduce the possibility of disk debris being left in theintervertebral space. This removal of disk material improves bone graftcontact and will improve fusion potential; and to minimize the degree oftissue trauma, by reducing the elapsed time and tool manipulationcurrently required to remove disk material and to prepare a site forbone grafting.

Additional advantages of the present invention will also become apparentfrom the accompanying detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a typical cutting device;

FIG. 2 is a side view of the cutting device of FIG. 1;

FIG. 3 is a partial detail view of the cutting device of FIG. 1illustrating the cutting head, including the angled blade configurationand the entry tip;

FIG. 4 is a cross-sectional view of the cutting head taken along line4--4 of FIG. 3;

FIG. 5 is a top view of a cutting device having an arrow style entry tipconfiguration;

FIG. 6 is an end view of the cutting device of FIG. 5;

FIG. 7 is a side view of the cutting device of FIG. 5;

FIG. 8 is a top view of a cutting device having a bullet style entry tipconfiguration;

FIG. 9 is an end view of the cutting device of FIG. 8;

FIG. 10 is a side view of the cutting device of FIG. 8;

FIG. 11 is a top view of a cutting device having a elliptical styleentry tip configuration;

FIG. 12 is an end view of the cutting device of FIG. 11;

FIG. 13 is a side view of the cutting device of FIG. 11;

FIG. 14 is a top view of the cutting device of FIG. 1 illustrating theapproximate length of the device for use in a non-cannulated open backsurgical procedure;

FIG. 15 is a top view of the cutting device of FIG. 1 illustrating therelational length of the device for use in a cannulated endoscopicsurgical procedure;

FIG. 16 is a top view of a alternative embodiment cutting device havinga rounded style entry tip configuration;

FIG. 17a is a side view of a drill guard for use in an open backsurgical procedure;

FIG. 17b is a side view of a drill guard for use in an endoscopicsurgical procedure;

FIG. 18 is a side view of a self-aspirating embodiment of the cuttingdevice of FIG. 1;

FIG. 19a is a top view of a round cutting head configuration of thecutting device;

FIG. 19b is a top view of a bulb cutting head configuration of thecutting device;

FIG. 20 is an end view of the cutting head of FIG. 19b having a roundedstyle entry tip configuration;

FIG. 21a is a top view of a cervical version of the cutting device;

FIG. 21b is a side view of the cutting device of FIG. 21a;

FIG. 22 is a top view of a cutting device illustrating an alternatetapered shaft configuration;

FIG. 23 is a side view of the cutting device of FIG. 22 including abearing or bushing;

FIG. 24 is a side view of a cutting device including multiple bearingsand a mechanical depth stop;

FIG. 25 is a side view of a cutting device including a full lengthbearing or bushing;

FIG. 26 is a cross-sectional side view of a cutting device captivewithin a cannula;

FIG. 27 is a cutting device with a screw shaft;

FIG. 28 is a cross-sectional side view of a modified arrow tip cuttinghead configuration taken along line 28--28 of FIG. 28A;

FIG. 28A is an end view of the cutting head of FIG. 28;

FIG. 29 is a top view of an auger tip cutting head configuration of thecutting device;

FIG. 29A is an end view of the cutting head of FIG. 29;

FIG. 30 is a top view of an additional modified arrow tip cutting headconfiguration;

FIG. 30A is an end view of the cutting head configuration of FIG. 30;

FIG. 31 is a top view of a modified elliptical cutting headconfiguration;

FIG. 32 is a top view of a modified rounded cutting head configuration;

FIG. 33 is a top view of a notch cutting head configuration;

FIG. 34 is a top view of a flame cutting head configuration;

FIG. 35 is a top view of a fluted cutting head configuration;

FIG. 36 is a top view of a rasp cutting head configuration;

FIG. 37 is a top view of a cutting head configuration with three cuttingblades formed by the window in the cutting head;

FIG. 38 is a cross-sectional end view taken along line 38--38 of FIG.37; and

FIG. 39 is a cross-sectional end view of a cutting head configurationhaving four cutting blades formed by the window in the cutting head.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, the surgical cutting device 10 of thepresent invention is shown. The surgical cutting device comprises amounting shaft 12, a main shaft 14 attached to the mounting shaft, and acutting head 16 positioned at the opposite end of main shaft 14. Themain shaft can include optional engraved depth indicators 18 positionedadjacent to the cutting head. Although the cutting device functionsproperly without the depth indicators, they do add a certain degree ofvisualization during surgery. The cutting head, main shaft, and mountingshaft are an integral piece of hardened surgical steel, wherein themounting shaft is connected to a rotary drill so that the cutting devicecan be rotated allowing the cutting head to operate. Alternatively,since the cutting head, main shaft, and mounting shaft are of differentdiameters, the components can be milled from different diameter rodstock and then braised or welded together through a socket or buttjoint. Milling from different diameter rod stock is a more efficient useof rod stock which reduces waste and provides an easier milling processfor mass production.

Referring to FIGS. 3 and 4, the components of the cutting head 16 areshown in greater detail. The cutting head includes a window 20 machinedthrough the cutting head defining two cutting blades 22 on a leadingedge of the cutting head as the cutting device is rotated in acounterclockwise direction 24. Window 20 is machined through the cuttinghead defining angled walls 26 through the depth of the cutting head.Walls 26 are at an angle α approximately 15°-30° from a horizontal planeextending perpendicular to the opening of the window. The cutting bladescan be smooth as shown in FIG. 3 or serrated. Window 20 provides an areafor removed tissue to accumulate and be further reduced in density, dueto the rotation of the cutting blades. The removed material isessentially liquefied and removed by aspiration. It is to be understoodthat for a cutting device rotatable in a clockwise direction, theconfiguration of the cutting blades and tapered walls would be a mirrorimage of that depicted in FIG. 4. The window 20 as shown in FIGS. 1-4 iselliptical or oval in shape, however, other shaped windows arecontemplated as discussed subsequently herein. It is to be understoodthat all cutting head versions disclosed herein include a windowdefining at least two cutting blades as shown in FIGS. 3 and 4.

Another important aspect of the cutting head is the entry tipconfiguration 28. FIGS. 5-7 illustrate an arrow style entry tip 30 forthe cutting device 10. The arrow style entry tip has an ellipticalperimeter 32 with a converging sloping surface 34 which converges in arounded point 36. FIGS. 8-10 illustrate an alternative entry tipconfiguration being a bullet style entry tip 38. The bullet style entrytip includes a circular outer perimeter 40 having a sloping convergingsurface 42 terminating in a rounded point 44.

FIGS. 11-13 illustrate a second alternative entry tip configurationbeing an elliptical style entry tip 46. Elliptical style entry tip 46includes an elliptical perimeter 48 with an arcuate rounded outersurface 50.

The cutting device of the present invention has dimensions that arepractical for entry into the spinal intervertebral disk space for thevarious regions of the spine. The typical outside diameter or width ofthe cutting head will range from about 3 to about 13 millimeters. Widthsof the cutting head can also range from about 5 to about 9 millimeters.The cutting head is balanced around the axis of the device so that thedevice will not wobble during rotation.

As seen best in FIG. 14, the typical length of the cutting device 10 ofthe present invention for use in a non-cannulated fashion is from about3 inches to about 6 inches. This length provides the necessary shaftlength for insertion into a surgical drill and drill guard. The mountingshaft 12 of the cutting device has a reduced diameter from the mainshaft 14 for insertion into the surgical drill collet 52.

FIG. 15 illustrates the typical length of the cutting device for use ina cannulated, endoscopic fashion and is from about 8 inches to about 12inches. This length provides the necessary main shaft 14 length forinsertion into the surgical drill, a standard surgical cannula and anelongated guard (see FIG. 26) and provides the necessary extension ofthe entry tip 28 from the cannula for entry into the intervertebraldisk. The outside diameter of the cannulated endoscopic device is thatnecessary to fit in close tolerance with the inside diameter of astandard guard or surgical cannula.

The length of all embodiments of the cutting device of the presentinvention typically could increase in increments of 1/2 inch. Themounting shaft diameter 12 typically would be 0.092 inches or 0.125inches based upon currently available surgical drill mounting collets52.

FIGS. 17a and 17b illustrate standard surgical drill guards, whereinFIG. 17a depicts an open back surgery drill guard 54 and FIG. 17bdepicts an endoscopic surgery drill guard 56. The difference betweendrill guards 54 and 56 is the overall length of the guard. Guards 54 and56 are made of surgical steel tubing that slides onto the collet 52 ofthe drill and is held in place by friction. More specifically, guards 54and 56 include a friction sleeve 58 which slides over the drill collet52. Drill guards 54 and 56 further include a finger pull 60 forinsertion and removal of the drill guard and a guard body 62 extendingfrom the finger pull 60. A stabilizer bushing 64 is positioned at theend of the guard body 62. A shaft opening 66 extends along the length ofthe guard for insertion of the cutting device. Vent holes 68 aretypically located along the length of the guard body 72 at givenintervals. Standard commercially available guards or custom made guardsthat are slightly longer and have a slightly larger internal diametermay be used with the cutting device of the present invention.

FIG. 18 illustrates a self-aspirating cutting device 70 which includesan aspiration channel 72 extending along the length of the mountingshaft 74, main shaft 76 and terminating at window 80 in cutting head 78.The aspiration channel terminates in openings 82 and 84, in the windowof the cutting head and in the mounting shaft, respectively. Theaspiration channel of the cutting device is for aspiration of theremoved material.

The geometrical shape of the cutting head can also be varied. Thecutting head 16 of the cutting device embodiments referenced hereinillustrate a generally elliptical cutting head. Alternative cutting headgeometries can be seen in FIGS. 16, 19A and 19B. FIG. 16 illustrates atear drop cutting head configuration 86 having a rounded entry tip 88and includes converging walls 90 extending from entry tip 88 to mainshaft 92. In the tear drop configuration the cutting head includes atear drop shaped window 94. FIG. 19a illustrates a round cutting headconfiguration 96. In this configuration the cutting head includes arounded outer wall 98 extending from the main shaft 100. The roundcutting head also includes a circular window 102. FIG. 19b illustrates abulb cutting head configuration 104 having a rounded entry tip 106 andgenerally parallel side walls 108. Converging back walls 110 extend fromthe main shaft 112 to the parallel side walls 108. The bulb cutting headconfiguration includes a generally elliptical or oval window 114. Ineach of the tear drop cutting head configuration, round headconfiguration, and bulb head configuration, the entry tips have arounded configuration as shown in FIG. 20. The rounded entry tipincludes an oval perimeter 116 and a rounded outer surface 118.

FIGS. 21A and 21B illustrate a cervical cutting device 120 wherein themounting shaft 122 and main shaft 124 are of equal diameter. Thecervical cutting tool preferably would have an overall length of 3.75inches and a cutting head diameter of 0.125 to 0.160 inches. As seen inFIG. 21B, the height of the cutting head 126 is equal to the diameter ofthe main shaft.

FIGS. 22 and 23 illustrates yet another alternative cutting device 128having a tapered main shaft 130 without fillets at the juncture betweenthe main shaft and the mounting shaft 132. Cutting device 128, by havinga tapered main shaft, provides a design having improved strength androtational stability for longer shaft lengths. Longer shaft lengthcutting devices are particularly useful when the cutting device is usedin conjunction with a cannula.

When the cutting device is used with a cannula, a bushing or bearing 134is placed along the main shaft 130 to reduce the friction between themain shaft and the cannula into which the cutting device is inserted. Ifa bushing is used, it is preferably made from metal or plastic. If abearing were used, it would be a ball or race type bearing. Multiplebearings or bushings 134 and 136 can be utilized along the main shaft138 of a cutting device 140 as shown in FIG. 24. Although two bearingsor bushings 134 and 136 are shown, it is to be understood that anymultiple number of bearings or bushings having varying lengths can bepositioned along the main shaft of the cutting device to reduce frictionbetween the cutting device and a cannula.

A mechanical depth stop 142 can be incorporated into the cutting devicetypically at the juncture between the main shaft 138 and the mountingshaft 144 to prevent the cutting device from extending too far from theend of the cannula (see FIG. 26) when in use. Alternatively, instead ofutilizing one or multiple bearings or bushings, a full length bushing orbearing 146 can be positioned on the main shaft 148 of a cutting device150 as shown in FIG. 25.

The cutting device 150 can be removable from the cannula 152 or can becaptive within the cannula as shown in FIG. 26. When in a captiveconfiguration, the cannula 152 (or a surgical guard in otherapplications) includes retainer rings 154 and 156 at opposite ends ofthe main shaft 158 to rigidly secure the cannula to the main shaft. Twobearings or bushings 160 are positioned within the cannula, however itis to be understood that the number and length of each bearing orbushing can vary for the particular application.

FIG. 27 illustrates an alternative embodiment main shaft configurationfor a cutting device 162. The main shaft 164 is threaded 166, whichassists in moving displaced emulsified disk material from the cuttinghead, up the main shaft 164 and away from the surgical site. Althoughcutting device 162 is only shown in FIG. 27, it is to be understood thatdevice 162 is used in conjunction with a cannula or drill guard as shownin FIG. 26 for device 150. The threads 166 move the removed tissue alongthe shaft 164 within the cannula or drill guard.

FIGS. 28 through 36 illustrate additional cutting head configurationsfor the cutting device. FIG. 28 illustrates a modified arrow tip cuttinghead configuration wherein semi-circular portions 170 are removed fromthe entry tip, thereby defining semi-circular cutting blades 174positioned on either side of the entry tip 172. Cutting blades 174 onthe entry tip provide a smoother entry into the intervertable disk spaceand a more rapid removal of matter. FIGS. 29 and 29A illustrate an augertip cutting head configuration wherein the entry tip includes a narrowpyramidal entry portion 176 and angled base portions 178 and 180. Ablade 182 is machined onto the leading edge of the pyramidal centerportion 176. Blade 182 also provides a smoother entry into theintervertebral disk space and rapid removal of matter. FIG. 30illustrates a second modified arrow tip configuration in which asemi-circular and angled portion 184 is removed from each end of theentry tip to form a cutting blade 186 having a semi-circular portion 188and an angled relief portion 190. Semi-circular and angled portion 184provide a more aggressive cutting action for the cutting device.

FIGS. 31 and 32 illustrate modified elliptical and round cutting headconfigurations, respectively wherein the window 192 has been raised sothat the window 192 forms a thin portion 194 along the upper perimeterof the entry tip thereby extending the cutting blade around the upperperimeter 196 in the window. By moving the window upwardly, the cuttingblade is not limited to just the sides of the window and allows for theeasy removal of disk material using a lateral movement of the cuttingdevice across the intervertebral disk space.

FIG. 33 illustrates a notched cutting head configuration wherein eachside of the cutting head includes serrations 198. FIG. 34 illustrates aflame shaped cutting head configuration 200. FIG. 35 illustrates afluted cutting head configuration 202 wherein the cutting head includesraised spiral flutes or helixes 204 circling the diameter of the head.FIG. 36 illustrates a rasp cutting head configuration 206 wherein thecutting head is knurled producing smaller flutes 208 and 210criss-crossing in both directions around the diameter of the cuttinghead. The cutting head configurations of FIGS. 33 through 36 allow forthe easy removal of matter using a lateral movement of the cutting headacross the intervertebral disk space, and in particular the flutes ofFIGS. 35 and 36 provide for the head to be more aggressive in theremoval of material. Additionally, any of the cutting headconfigurations depicted herein can be diamond coated by dipping thecutting heads into a diamond emulsion to enhance the cuttingcapabilities of the device.

The cutting device of the present invention can also be designed toinclude three or more cutting blades on leading edges of a window in thecutting head. As seen in FIGS. 37-39, three and four cutting blades areshown. A device with additional cutting blades can be used whereadditional cutting action is desired. However, adding cutting bladesdoes involve more complex configurations that can be more difficult andexpensive to manufacture.

The cutting device 212 of FIGS. 37 and 38 illustrate a three bladedconfiguration wherein the cutting head 214 includes a window 216machined through the cutting device defining three cutting blades 218A,218B, 218C on a leading edge of the cutting head as the cutting deviceis rotated in a counterclockwise direction 220. Window 216 is preferablyformed using an EDM wire (electrical discharge machine) to electricallyremove material to form the window and blades. Other standard machiningprocesses can also be used such as, for example, milling. Window 216 ismachined to define angled walls 222 and a relief portion 224.

FIG. 39 illustrates a cutting device 226 having four cutting blades228A, 228B, 228C and 228D spaced around the circumference of a window230 of the cutting head 232. Cutting device 226 is similar to device 212except the cutting blades are slightly smaller to accommodate theadditional blade. Preferably, all of the cutting blades are of equalsize and uniformly spaced around the circumference of the cutting head,however, it is contemplated that the cutting blades could be ofdifferent sizes and nonuniformly spaced around the circumference of thecutting head but only in configurations where the combination of sizeand position ensures that the cutting device does not wobble duringrotation.

It is to be understood that the invention also contemplates versionshaving more than four cutting blades spaced around a window of thecutting head. All of the cutting devices with three or more blades onleading edges of a window can include any of the features discussedabove with respect to a two-bladed version, such as, for example, shaftstyles, head and entry tip shapes, use with cannulas or guards, and canbe formed from a single piece of surgical steel or multiple piecesjoined together.

Although the present invention has been described and is illustratedwith respect to various embodiments thereof, it is to be understood thatit is not to be so limited, since changes and modifications may be madetherein which are within the full intended scope of the invention ashereinafter claimed.

What is claimed is:
 1. A cutting device for removing matter from asurgical site during a surgical procedure comprising:means foremulsifying the matter during the surgical procedure said emulsifyingmeans including an entry tip portion and at least three cutting bladeslocated one each on opposed leading edges of a window extending throughthe emulsifying means such that each cutting blade faces in the samedirection of rotation, said entry tip portion having a cutting edgeadjacent an outer surface thereof to facilitate entry into the matter;and means for rotatably supporting the emulsifying means during thesurgical procedure.
 2. The cutting device of claim 1 wherein the windowin the emulsifying means defines at least three walls extending at anangle from each cutting blade.
 3. The cutting device of claim 2 whereinthe support means comprises a main shaft and a mounting shaft, themounting shaft having a diameter adapted for insertion into a surgicaldrill.
 4. The cutting device of claim 3 wherein the main shaft, mountingshaft and cutting head are formed from a single piece of hardenedsurgical steel.
 5. The cutting device of claim 1 wherein saidemulsifying means has a center of gravity located at a central axisextending along a length thereof.
 6. The cutting device of claim 1wherein the cutting edge on the entry tip is semicircular.
 7. Thecutting device of claim 1 further comprising means for protecting anarea adjacent the surgical site.
 8. The cutting device of claim 7wherein the means for protecting an area adjacent the surgical site is acannula.
 9. The cutting device of claim 8 wherein the means forprotecting an area adjacent the surgical site is a drill guard.
 10. Thecutting device of claim 8 further comprising means for reducing frictionbetween the main shaft and the cannula.
 11. The cutting device of claim10 wherein the means for reducing the friction is at least one bushing.12. The cutting device of claim 10 wherein the means for reducingfriction is at least one bearing.
 13. A cutting device for removingmatter from a surgical site during a surgical procedure, whichcomprises:means for emulsifying the matter during the surgicalprocedure; said emulsifying means including an entry tip and at leastthree cutting blades located one each on opposed leading edges of awindow extending through the emulsifying means such that each cuttingblade faces in the same direction of rotation; means for rotatablysupporting the emulsifying means during the surgical procedure; and aguard for sliding onto a collet of a drill, said guard having an openingextending along a length thereof for insertion of said supporting means.14. A cutting device for removing matter from a surgical site during asurgical procedure comprising:means for emulsifying the matter duringthe surgical procedure; said emulsifying means including a cutting headhaving an entry tip and at least three cutting blades located one eachon opposed leading edges of window extending through the cutting headsuch that each cutting blade faces in the same direction of rotation,said entry tip having at least one cutting blade positioned on an outersurface of said entry tip, said cutting blade on said entry tip being araised spiral flute circling a diameter of said cutting head; and meansfor rotatably supporting the emulsifying means during the surgicalprocedure.
 15. A cutting device for removing matter from a surgical siteduring a surgical procedure comprising:means for emulsifying the matterduring the surgical procedure; said emulsifying means including acutting head having an entry tip and at least three cutting bladeslocated one each on opposed leading edges of window extending throughthe cutting head such that each cutting blade faces in the samedirection of rotation, said entry tip having a plurality of cuttingblades on an outer surface of the entry tip, the cutting blades beingcriss-crossing spiral flutes circling a diameter of the cutting head;and means for rotatably supporting the emulsifying means during thesurgical procedure.
 16. A cutting device for removing matter from asurgical site during a surgical procedure which comprises:means foremulsifying the matter during the surgical procedure; said emulsifyingmeans including an entry tip and at least three cutting blades locatedone each on opposed leading edges of a window extending through theemulsifying means so that each cutting blade faces in the same directionof rotation; and a support member for rotatably supporting theemulsifying means during the surgical procedure, the support memberhaving a main shaft and a mounting shaft, the main shaft being threaded,the mounting shaft having a diameter adapted for insertion into asurgical drill.
 17. A surgical apparatus for cutting tissue, whichcomprises:an elongated shaft having proximal and distal ends anddefining a longitudinal axis, the elongated shaft adapted for rotationalmovement about the longitudinal axis; and a cutting head disposedadjacent the distal end of the elongated shaft and adapted forrotational movement therewith, the cutting head having at least threecutting elements arranged about the longitudinal axis to define anopening therebetween for at least partial reception of hard tissue, thecutting elements each defining a leading cutting edge dimensioned andconfigured to cut tissue upon rotation of the cutting head in a firstrotational direction, the cutting head further including an entry tipportion disposed distal of the cutting elements, the entry tip portiondefining an entry cutting edge dimensioned to cut bony tissue tofacilitate entry of the cutting head within the tissue.
 18. The surgicalapparatus of claim 17 wherein the cutting edges of the cutting elementsare in general parallel relation with the longitudinal axis of theelongated shaft.
 19. The surgical apparatus of claim 17 wherein thecutting elements and the entry tip portion are the sole cutting elementsof the cutting head.
 20. The surgical apparatus of claim 17 wherein thecutting elements of the cutting head are symmetrically arranged aboutthe longitudinal axis.
 21. The surgical apparatus of claim 17 whereinthe elongated shaft includes a groove defined in an outer surfacethereof dimensioned to convey tissue removed by the cutting head in aproximal direction.
 22. The surgical apparatus of claim 17 wherein thecutting edges of the cutting elements are dimensioned and configured tocut intervertebral disc material.
 23. The surgical apparatus of claim 17wherein the cutting edges of the cutting elements are dimensioned andconfigured to at least partially emulsify the tissue.
 24. The surgicalapparatus of claim 17 wherein the elongated shaft defines an aspiratingchannel to convey tissue removed by the cutting head in a proximaldirection.